1. Field of the Invention
This invention relates aqueous treatment compositions for use as an anti-scalant and dispersant. Further, this invention relates to polymers for use in such compositions. More specifically, this invention relates to polymers containing low amounts of sulfonate and their use in aqueous treatment compositions, including scale minimization.
2. Background Information
There are many aqueous industrial systems that require various materials remain in a soluble, or suspended, or dispersed state. Examples of aqueous systems include boiler water or steam generating systems, cooling water systems, gas scrubbing systems, pulp and paper mill systems, desalination systems, fabric, dishware, hard surface cleaning systems and downhole systems encountered during the production of gas, oil, and geothermal wells. In many cases, water contains (either naturally or by contamination) ingredients such as inorganic salts, which can cause accumulation, deposition, and fouling problems. These salts are formed by the reaction of metal cations such as calcium, magnesium or barium with inorganic anions such as phosphate, carbonate and sulfate. The salts formed have low solubility in water. As their concentration in solution increases or as the pH or temperature of the water containing them increases, the salts tend to precipitate from solution, crystallize and form hard deposits or scale on surfaces. Scale formation is a problem in equipment such as heat transfer devices, boilers, secondary oil recovery wells, and automatic dishwashers, as well as on substrates washed with such hard waters.
Many cooling water systems made from carbon steel experience corrosion problems, including industrial cooling towers and heat exchangers. Corrosion is combated by the addition of various inhibitors such as orthophosphate compounds and/or zinc compounds. However, phosphate addition increases the formation of highly insoluble phosphate salts such as calcium phosphate. The addition of zinc compounds can also lead to the precipitation of insoluble salts such as zinc hydroxide, and zinc phosphate. Further, other inorganic particulates such as mud, silt and clay are commonly found in cooling water. These particulates tend to settle onto surfaces, thereby restricting water flow and heat transfer unless they are effectively dispersed.
Stabilization of aqueous systems containing scale-forming salts and inorganic particulates involves a variety of mechanisms. One stabilization mechanism is dispersion of precipitated salt crystals due to adsorption of the inhibitor onto precipitated crystals. Adsorption of the inhibitor can also stabilize the system by facilitating the dispersion and subsequent removal of other suspended particulates from aqueous systems such as mud, silt and clay, and metals such as iron and zinc and their insoluble salts. Another stabilization mechanism involves interference and distortion of the crystal structure of the scale by the inhibitor, making the scale less adherent to surfaces or other forming crystals or existing particulates.
In aqueous drilling mud, a dispersant's ability to deflocculate and disperse flocculated and agglomerated solids is highly desired, especially in electrolyte-rich fluids. Conventionally used polyacrylates are known to be sensitive to divalent cations, which may be introduced into drilling fluid through electrolyte-releasing formations containing gypsum, lime and other salt deposits, or through the water used in formulating the mud (e.g., sea water). Accordingly, there is a need for products that provide rheological stability to polyelectrolyte-containing drilling mud, particularly to high solids mud (i.e., having densities greater than 15 pounds per gallon).
In ferro-cement compositions, polymeric additives are employed that improve physical characteristics, e.g., flow and workability. These additives, often referred to as ‘plasticizers’, also improve the flow characteristics of the compositions containing them, enabling the cement compositions to be pumped or poured effectively and fill all spaces in a mold or other structure. Such additives can also be used in designing ferro-cement compositions having reduced water content but still retaining adequate flow properties.
In cleaning compositions polymers can impart many useful functions. For example, they can function either independently or concurrently as viscosity reducers in processing powdered detergents. They can also serve as anti-redeposition agents, dispersants, scale and deposit inhibitors, crystal modifiers, and/or detergent assistants that are capable of partially or completely replacing materials used as builders while imparting optimum detergent action properties to surfactants.
Recent trends have been to reduce or eliminate the use of inorganic phosphates due to environmental pollution problems. In this regard, a variety of other methods of water softening have been employed, of which one of the most economical is the addition of alkali metal carbonate salts. However, these salts are effective by removing hardness ions via precipitation, thereby leaving unacceptable levels of residue on washed articles. Accordingly, there is a need for polymers that exhibit both superior threshold inhibition (i.e., they maintain hardness ions in solution past their normal precipitation concentration) and crystal modification (which can prevent the unacceptable levels of residue adhering on the washed articles).
Polymers have found wide utility in machine dishwashing applications by performing many of the same functions as in fabric laundering formulations. However, these polymers may be required to perform different functions due to differences between dishwashing and fabric formulations, the substrates being cleaned, and the machines themselves. Polymers are added in order to disperse particulate matter and prevent soils that have been removed from the article from agglomerating and re-adhering to the surface of the cleaned article, as well as minimize filming and spotting of the substrate. Machine dishwasher formulations differ from home laundry compositions in one respect in that most dishwashers require higher wash temperatures. Dishwashing machines typically utilize internal heating elements to increase the temperature of the water to optimum operating temperature. Under these conditions, the heating element can form surface deposits that significantly reduce its efficiency. Polymers that are able to remove these deposits are thus often added to machine dishwasher formulations. These polymers must be hydrolytically stable at the higher wash temperatures, as well as the pH conditions encountered in these systems.